Learn Farsi: منظور من توهین کردن نبود، بلکه از پروژه‌ی شما انتقاد کردم. - My intention was not to insult, but rather I criticized your project.

The word balkeh is used specifically for "corrective contrast" after a negative statement. Because the first half of the sentence tells us what the intention was not (nabood), we use balkeh to introduce the actual truth (meaning "but rather"). Words like vali and amma just add contrasting information, whereas balkeh completely replaces a negated idea with a new fact.

Why is there an az (from) before prozheh-ye shoma?

The compound verb enteghaad kardan (to criticize) specifically requires the preposition az to indicate the thing being criticized. In Farsi, you literally say "I did criticism from your project."

Why is tohin kardan (to insult) in its full infinitive form rather than conjugated?

Here, the infinitive is acting as a noun (a gerund), meaning "insulting" or "the act of insulting." The literal translation of the first half is "My intention was not insulting." Using the full infinitive emphasizes the action itself, though you could also just use the simple noun tohin (insult).

Why is a "ye" sound added to the end of prozheh?

This is the Ezafe, which links a noun to its possessor. Because prozheh ends in a silent "heh" (which sounds like an "e"), we must add a spoken "ye" sound (prozheh-ye) to smoothly connect it to . You see a simpler Ezafe at the very beginning of the sentence with (intention of me).